I'm honestly suprised that you haven't changed the cat-back portion yet. Usually a 2.25" or 2.5" exhaust is recommended (I have the 2.25"). You may not be able to feel a difference, but the sound change would be amazing. I can only imagine how bad the Kami sounds w/ stock cat-back. Although, I do know how crappy it sounds w/o a muffler (basically straight piped). Loud as all get out and more fart sounds than a full Mexican restaurant. lol

What do you have done to the rest of the exhaust? I've got the Kamikaze and I love it. I've got a resonator in-line before a Borla Pro-XS muffler. It's got a slight rasp around 3 or 3.5k, but other than that it sounds yummy.